There's a section for track building with tips and things.
I do it by putting a barge for example and a fence or whatever, next to it. So the barge is on it's side (half in the ground) then you link them in a template using the fence bit as the main part. Then delete them, go to your templates and load it up. You will then be able to rotate both props on the fence props axis, making the barge go lower/higher/whateverer than usual (it can take some fiddling to get to the right height). After that you just delete the fence prop and you have your new kerb!
Not the best at explaining it but hope it helps. You may have better luck in the content creator area =)